GB2052597A - Flue Blocks - Google Patents

Abstract

A hollow, tubular flue block 10 has a projecting spigot 14 at its lower end which forms a rim around the aperture 12 through the block. The spigot mates with a corresponding recess 22 at the upper end of a similar block. The spigot 14 projects by a distance greater than the depth of the recess 22, so that blocks can be dry jointed to leave a peripheral groove 24 into which cement is subsequently grouted. This decreases the risk of cement falling into the aperture 12 during construction of the flue. <IMAGE>

Description

SPECIFICATION Flue Blocks This invention relates to flue blocks.

It is known to provide a flue within a skin of a wall by incorporating as a part of the skin a column of blocks which are of hollow tubular construction. The blocks are laid one on top of each other with their hollow interiors in communication to form the flue.

One reason why such flue blocks have been found not to be entirely satisfactory in practice is that there is a danger that when the flue blocks are cemented into a column the cement placed in the joints between them will pass into the flue itself, and tend to block it unless great care is taken. In their desire to avoid this, it is not uncommon for labourers to use too little cement in the joints, so that the joints are structurally unsound amd may also permit gases to escape from the flue. Flue blocks are known in which an upstanding rim, perhaps about 1 cm high, is provided around the top of the aperture, with an exactly corresponding recess at the other end of the aperture to receive an identical upstanding rim of an adjacent flue block. Such rims serve to locate the blocks in the column.They also help to prevent the ingress of cement into the aperture, but they are by no means completely successful in this. A further point is that the cement used between the blocks has to fulfil strict requirements of heat and acid resistance, because it is likely to come in contact with the flue gases and because acidic condensates from the flue gases tend to collect in the joints between the blocks.

According to one aspect of the present invention there is provided a flue block having an aperture therethrough from one end face to the opposite end face so that it is of hollow tubular form, there being a spigot projecting from one end face forming a rim around one end of the aperture, the opposite end face having a recess forming an enlarged entrance to the aperture to accommodate a corresponding spigot of an adjacent flue block, the spigot projecting further than the depth of the recess so that when two such flue blocks are abutted with the spigot of one inside the recess of the other, the adjacent end faces are spaced apart to form a peripheral groove into which cement or another jointing composition can be grouted.It is therefore possible to form a flue by dry jointing two or more such flue blocks together with the spigot of one in the recess of the next, so that there is no necessity to apply cement before abutting the flue blocks, and the danger of cement falling down inside the block is minimised.

According to a second aspect of the invention there is provided a method of forming a flue, comprising abutting two or more flue blocks as defined above, with the spigot of one inside the recess of the other, and subsequenty grouting cement or another jointing composition in the peripheral groove formed.

In order that the invention may be better understood, a flue block will now be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 is a side view of the flue block, Fig. 2 is a cross-section on the line Il-Il of Fig.

1, Fig. 3 shows parts of two such flue blocks showing how they are jointed, and Fig. 4 is a horizontal cross-section through a cavity wall incorporating a flue formed from such flue blocks.

Referring firstly to Figs. 1 and 2, the flue block 10 is cast from cementitious material with an aperture 1 2 therethrough between the two end faces 16,20 of the block, so that it is of hollow tubular form. From the lower end face 1 6, there projects a spigot 14 which forms a rim around the aperture in the lower end face 1 6 of the flue block 10. The spigot is parallel sided, but it has a free end portion externally tapered at 1 8. In the opposite, upper end face 20 of the flue block 10, there is a tapering recess 22 around and leading into the aperture 12. The taper of the recess 22 matches the taper 1 8 of the spigot 14. As seen in Fig. 3, this enables two flue blocks 10 to be abutted, with the taper 18 of one nesting in the recess 22 of the other.The spigot 14 is longer than the depth of the recess 22, so that when two flue blocks 10 are nested in this fashion the adjacent end face 16,20 are spaced apart to leave a peripheral groove 24.

In use, therefore, a flue is formed by nesting several such blocks 10 in this manner, with the spigots 14 lowermost, the joint between adjacent blocks being initially dry. Subsequently, cement is grouted into the peripheral groove 24. This provides a structural strength to the joint, and also the necessary sealing to prevent the escape of flue gases through the joint.

Fig. 4 shows how the flue blocks are used to form a flue within the inner skin of a normal cavity wall. The wall comprises an outer skin 26, and an inner skin 28, both formed of brickwork in the usual manner, and with a cavity 30 between them. The flue blocks 10 are built into the inner skin of the wall in place of bricks. Conventional galvanised steel wall ties 32 span the cavity between the inner and outer skins 26 and 28 on either side of the line of the flue blocks 10. This is desirable because the flue blocks 10 are of course located one above the other, rather than being interleaved in the usual brickwork manner.

The cement grouted into the peripheral groove 24 will usually be a high alumina cement, in order to withstand the heat associated with the flue gases passing up the flue. The cementitious material of which the blocks 10 are made is suitably a concrete made from power station clinker, pulverised fuel ash, sand, high alumina cement, and with a proportion of glass fibres to give the material strength. Such a glass reinforced cementitious material is particularly desirable to prevent accidental breakage of the projecting spigot 14. In place of the power station clinker and pulverised fuel ash, it is possible to use commercially available aggregates such as those sold under the Trade Marks Lytag and Aglite.

Because of the fact that the cement can be grouted into the peripheral groove 24 after the blocks 10 have been dry jointed together, there should be no danger of the jointing cement falling within the aperture 12 and causing a blockage.

Moreover, there is no temptation for the labourer to use less cement than is required in an attempt to prevent this, and so it is easy to ensure that the joint does not permit the leakage of the flue gases. A further advantage is that it is not necessary for the spigot 14 to be at the upper end of the block when it is laid (as would be necessary if cement were being applied to the upper face of the block prior to positioning the next block, in order that the spigot reduces the amount of cement falling into the aperture 12). This means that the joint between the taper 1 8 and recess 22 slopes upwardly away from the aperture 12, so that if flue gases condense inside the flue, they do not run into and collect in the joint. Therefore the prob!em of acidic condensates tending to reduce the effectiveness of the joint in time is minimised.

Claims (11)

Claims

1. A flue block having an aperture therethrough from one end face to the opposite end face so that it is of hollow tubular form, there being a spigot projecting from one end face forming a rim around one end of the aperture, the opposite end face having a recess forming an enlarged entrance to the aperture to accommodate a corresponding spigot of an adjacent flue block, the spigot projecting further than the depth of the recess so that when two such flue blocks are abutted with the spigot of one inside the recess of the other, the adjacent end faces are spaced apart to form a peripheral groove into which cement or another jointing composition can be grouted.

2. A flue block according to claim 1 wherein the spigot has a free end portion which is externally tapered, and the recess is correspondingly tapered to lead into the aperture.

3. A flue block according to claim 1 or claim 2, made from a concrete comprising cement and an aggregate.

4. A flue block according to claim 3 wherein the cement is high alumina cement.

5. A flue block according to any one of the preceding claims made from a cementitious material including a proportion of glass fibres.

6. A flue block substantially as described herein with reference to the accompanying drawings.

7. A method of forming a flue, comprising abutting two or more flue blocks according to any one of the preceding claims, with the spigot of one inside the recess of the next, and subsequently grouting a jointing composition in the peripheral groove formed.

8. A method according to claim 7 in which the spigot of each block is lowermost and the recess uppermost.

9. A method according to claim 7 or claim 8 wherein the jointing composition is high alumina cement.

10. A method of forming a flue, substantially as described herein with reference to the accompanying drawings.

11. A wall having a flue therein made from flue blocks according to any one of claims 1 to 6 or by a method according to any one of claims 7 to 10.